Radio controlled watches are known in the past which receive a time code signal to correct their times. The time code has a predetermined format of successive frames of 60 seconds with each frame including 60 data pulses one occurring in a unit period of 1 second. The time code now in use in Japan includes a “P” signal that is high for 0.2 seconds from a start of a unit period, a “0” signal that is high for 0.5 seconds from a start of a unit period, and a “1” signal that is high for 0.8 seconds from a start of a unit period. Among these signals, the “P” signal is defined as a frame marker which indicates a start of each of the frames of the time code and serves also as a position marker which indicates each of divisions of data such as minutes, hours, day and year. Moreover, the “0” and “1” signals represent binary “0” and “1”, respectively, which can be applied to a time code format, thereby calculating a current exact time and date represented in minutes, hours, day, month, and year. The seconds is represented by a time point of a rise of each data pulse.
The time code, for example, AM-modulated, is carried by the standard signal, which is of 40 or 60 kHz, but a clear signal waveform indicative of the time code is difficult to receive due to diffused reflections/attenuations in buildings and mixing of turbulent noise. Especially, in the reception of the time code, about four frames or four-minute data of the time code is usually received to avoid wrong recognition of the time code. It is, however, difficult to continue to receive its clear signal throughout this duration time.
In the past, some propositions have been made which try to determine the time code accurately from the standard time and frequency signal even when the same contains noise. For example, Japanese Patent Application TOKKAIHEI 11-211858 discloses a technology that detects at intervals of 0.1 seconds whether the received signal is high or low, and determines a data pulse included in the signal, using its binarized data.
In the above-mentioned time code receiving and data pulse determining methods and when the detected signal contains a little noise, its data pulse is detectable from the binarized data of the detected signal. However, if the detected signal contains a considerable noise, the data pulse cannot be determined correctly.
An object of the present invention is to provide a time information receiver and radio controlled watch capable of determining a received data pulse accurately from the time code even when the same contains a considerable noise.